Question

If each term in a geometric sequence is defined as

an = -6. (-1)"-1
what's the sum of the first 20 terms of
the sequence?

A. 0
B. 6
C. 120
D. 15

Answer 1

A

Explanation:

`a_n=-6(-1)^(n-1)`

The first term is -6 and the common ratio is -1.

The sum is thus

`(6(1-(-1)^(20)))/(1-(-1))=0`